Patterns of self-administration of delta-9-THC (i.v.) by rhesus monkeys will be analyzed under conditions of mixtures with cocaine and phenobarbitol as well as other drugs. Food reinforcement and shock avoidance will also be related to THC intake in additional monkeys. Tolerance to behavioral effects and concomitant physiological activity resulting from chronic administration of delta-9-THC will be studied in rhesus monkeys. Other forms of marijuana, such as m.E.D. or constituents of the plant which may be revealed to be pharmacologically active by other laboratories, will be analyzed in the above preparations.